Nokia Asha 300 - Does my Nokia phone support subfolders and folders in Mail for Exchange?

Yes it does.

By default, your Inbox and Outbox folders are synced, but you can choose to sync also other folders.

To include more folders in the sync, do the following:

  1. Select Options > Manage Subscribed Folders.
  2. Mark the folders that you want to include in sync.
  3. Select Save.